If you have a Galaxy S5 on AT&T, today's the day you start checking your phone for an update. The carrier has started pushing out a 142.8MB update to phones today that fixes a whole bunch of things, including security patches, app install enhancements and UX fixes for the email app. The full list of improvements and fixes, according to AT&T's support pages:

If you haven't yet received the update, be on the lookout now that it's rolling out to everyone. Once you have received it, be sure to hop into the forums and let others know how the phone's working after the update.